Commutator-brush and method of making the same.



R. L. SEABURY.

COMMUTATOR BRUSH AND METHOD OF MAKING THE SAME. APPLICATION HLED JULY2]. 1914.

W1 TNESSES [NYE/v TOR Patented Sept. 19, 1916.

I is a specification.

UNIT STAS A'EN FFMYEQ RALPH LOWE SEALBURY, OFWELLSVIILLELNEW YORK.

I COMMUTATOR-BRUSH AND METHOD OF MAKING SAME.

iaaaeaa' To all whom it may concern:

Be it known that I, RALPH Lown SEA- BURY, a citizen .of the UnitedStates, residd ing at Wellsville, State of New York, have inventedcertain new and useful Improvements in Commutator-Br'ushes and Methodsof Making the Same, of .which the following The object of my inventionis the produc tion of an improved brush for use on commutators andcollector rlngs of dynamo electric machines which possesses goodelectrical characteristics and good Wearing qualities 2O ting heavycurrents and for use on low voltand a good mechanical construction.

More particularly my invention relates to brushes-that transmit heavycurrents to -or from the commutator and to brushes that y areemployed-at low voltages and includes not only the article but theprocess of making it. Heretofore brushes for transmitagemach-ineshavecommonly been made of superimposed strips of thin copper or othermetal or wire gauze (usually of bronze or of copper) properly rolled andflattened into a nearly solid mass oflthe desired shape. Such brusheshave not been-satisfactory on account of excessive commutator and vbrushwear.

Another method commonly 'used to make I brushes of high conductivity hasbeen to employ very finely divided copper or other metal such as wouldpass through a one hundred (100) mesh screen intimately mixed Y withfinely divided carbon and the wholemass then being bonded together withpitch and subsequently baked or carbonized.

This method is objectionable because too high a percentage of "copper ormetal is 40 necessary'in order to secure a high conductivity thus'reducing the percentage of carbon that can be used which results in atendency of the brush to wear away itself and the commutator.Furthermore, such brushes some-' times fail to operate on low. voltagework [.owing to a thin film or coating presumably' an oxid or carbiddeposited on its face or on i the commutator.

Still another method of making high con--' forms of brushes.

Specification of Letters Patent. Patented Sept. 19, 1916. Applicationfiled July 27, 1914. Serial No. 853,503.

ductivity brushes has been to employ alternatelayers of wire gauze, thestrands which would measure about .0107 in diameter and woven to aboutthirty (30) meshes per inch bonded :between -,stri-ps or carbon. Suchseparated and are open tothe further 0bjection' that the 's'trandsofwire frequently fuse andmelt away at the face of the brush 7 whentransmitting heavy currentscaused by the current being carried by acomparatively few number of wires thus greatly impairing.

the conductivity 'of the brush.

Various other forms and combinations of brushes have been devised butnone, so far as I amaware, has proved thoroughlyefiicient andsatisfactory, for carrying very heavy machines. Y My invention aims tocombine the high .currents' or for operation on low,volta'geconductivity of metal with the lubricating qualities of carbon withoutencountering the difficulties and objections attending the older Inmaking my brush I employ copper orother metal in the form of narrowribbons and exceedingly thin (about ,QOl in thickness) or preferablyfinely drawn wire about 003' in diameter, which preferably has been'cutinto short pieces. I

about'oneeighth-of an inch or if desired of about the same length as thethick- ,ness of the finished brush, then thoroughly mix these shortmetal filaments or ribbons with a certain percentage of finely groundcarbon and add enough pitch or other binder to hold the mass firmlytogether after having been properly compressed and baked or otherwisecured. It may be remarked that the conductivity will be mainly governedby the percentage of metal filaments or ribbons present in the mix andthat different commutating elfects may be secured by not only changingthe cross sectionof the metal filaments or ribbons themselves, eitherabove or below 'the dimensions given above but also by changing theirlengths as used in the mix.

In the preferred form of my invention I employ a mixture containingabout sixty per cent. of copper filaments, about twenty live per cent.of carbon and about fifteen per cent. of pitch. Any suitable method maybe employed in forming or compressin the mix into suitable form. Themethod which I ordinarilyemploy consists of molding the mix in suitablemolds under a pressure of about thirteen tons per square inch.

' of the particular forms that I have described of comparatively shortribbons or filaments in the mix, practically all the filaments orribbons will arrange themselves so that their major axis will lieparallel to the sides of the brush. I attribute the formation of thisarrangement to the fact that considerable air is expelled from the mixduring the process of molding which rapidly escapes laterally andfinally leaving between the walls of the mold and the plunger, the saidair in thus escaping forces the filaments to a great extent to arrangethemselves in a plane parallel to the face of the plunger. During theextrusioirprocess in a socalled jumbo such filaments or ribbons beingmuch longer than they are wide or thick,

. would on account of the dragging effect of the die, tend to forcesuch'elongated metallic particles to arrange themselves so that theirlength would lie in a plane parallel with the plane of the thickness ofthe brush, thus producing substantially the same effect in molding-thebrush. This is a very desirable arrangement since practically eachfilament at the face of the brush will present against the commutatorone of its ends; this construction secures a very low contact resistancebetween the commutator and the brush. in excellent electrical contactwith the ones adjacent to it, either by actual metallic contact orthrough a very thin medium of carbon, brushes of this construction havean exceedingly low specific resistance, one containing sixty per cent.filaments showing as low a resistance as brushes commonly made thatcontain eighty per cent. metal in the usual powdered form: This not onlyeffects a saving in metal, important particularly if silver, gold orother expensive metal is used, but also permits a much larger percentageof carbon to be used in the brush, the chief object of which is to actas a lubricant and to prevent abrasion or undue Wear- Furthermore, sincheach filament is ments and carbon such as I have previously described.

Numerous other modifications and combinations from the above descriptionwould of course be obvious to those skilled in the art.

In the accompanying drawings Figure 1, is an elevation showing thecompleted brush; Fig. 2, is an endview showing the ends of the metalfilament in the face of the brush;'

Fig. 3, illustrates an end view of a com posite brush while Fig. 4,shows a diagrammatic side View of a composite brush.

Referring to the drawing, A designates a brush in which the metallicparticles 1 are distributed throughout the body of the brush, beingembedded in the material 2 formed by the carbon and pitch, as shown inFig. l. The metallic particles 1 extend longitudinally of the brush,andin Fig. 2 only the ends of the particles lying in the end sur face ofthe brush are seen. In Figs. 3 and 4 a brush B is shown in which thecore is composed of metal particles embedded in carbon and pitch, andaround the .core is a covering 3 of carbon and pitch material.

The above described arrangements are deemed suflicient to illustrate thenature of my invention and are intended as enumera- .tions of all of itsmodifications.

This brush may be used in other situations where it is desired to changeor switch heavy currents or where a contact for low voltage work isdesired that Will minimize the voltage drop. This also may be'used as aself lubricating bearing material.

While I have hereinbefore described and illustrated the best form of myinvention now known to me, it is obvious that those skilled in the artmay make changes and modifications in the form of my invention withoutdeparting from its spirit.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. A commutator brush comprising a block of carbon, having embeddedtherein a quantity of fine metallic strands, said strands beingpromiscuously disposed throughout the block andthe strands beingsubstantially parallel with the major axis of the brush.

2. The herein-described process of making electric brushes, whichconsists in mixin'g carbon particles, a suitable binder, and metallicparticles of elongated form into a plastic mass, irvith the metalparticles pro- M to themselves and to the axis of the brush, and bakingthe brush.

July 24, 1914:.

RALPH LOWE SEABURY.

WVitnesses:

L. H. DAVIS, W. ll-RICHARDSON;

